It could soon be possible to test someone’s spit to check whether they have had a heart attack and need to go to the emergency room, suggests new research.
The test, which takes as little as 10 minutes to complete, could allow more people to be diagnosed quickly and by non-medics outside the clinic or hospital setting. It measures levels of a protein called troponin, which is a measure of cardiac damage and is present in higher amounts than normal in the body after heart attacks.
Roi Westreich, a researcher and clinician at the Soroka University Medical Center in Israel, developed the test with university colleagues and in conjunction with Salignostics – an Israeli biotech specializing in saliva-based rapid diagnostic technology.
“While the currently used standard blood-tests are considered accurate and reliable, they have several limitations,” he explained. “In addition to a delay of at least one hour for results, the analysis must be performed by professional lab technicians in an emergency rooms or hospitals.”
The advantage of the saliva test would be its speed and ease of use, as the test is straightforward and can be performed by anyone. The results are also easy to interpret and can be read in a similar way to a standard pregnancy test you can buy from a drug store.
“The goal is to use it at the point of care, meaning that patients with chest pain can be tested wherever they are without waiting to reach a hospital. This has the added benefit of sparing unneeded visits to the emergency room, an issue which has received worldwide attention during the Covid-19 outbreak,” added Westreich.
Normally, conclusive diagnosis of a heart attack requires a combination of someone having specific symptoms such as chest pain, and abnormal results from an electrocardiogram and a blood test to check troponin levels.
In this study, Westreich and colleagues tested saliva from 32 patients who had a confirmed heart attack with heart muscle damage, as well as 13 controls who had not.
Although a saliva test is quicker and less invasive for patients, it is not as easy a substance to test as blood. There are a lot of non-relevant proteins in the saliva that can make it harder to obtain an accurate result.
To try and get round this problem, the researchers working on this study tested a processing system that removed some of the non-relevant proteins in the sample before testing, which they found helped to boost test accuracy.
Assuming that the level of troponin in the saliva of someone with a heart attack would be above a certain level (100 ng/l) after processing, the test was able to accurately diagnose more than 82% of heart attacks, although some people in the control group falsely tested positive.
Importantly, among those who tested negative on the test less than 2% were incorrectly diagnosed, which means the test could be a good way to check if someone needs to go to the ER or see a cardiologist to get further tests to confirm the diagnosis.
Westreich says that while these results are promising, “further research is needed to determine how long troponin stays in the saliva after a heart attack.”
Salignostics was set up in 2016 and already has a saliva-based pregnancy test on the market. In addition to developing a cardiac test, the company is working on saliva-based tests for infectious diseases such as Covid-19, malaria and the ‘bad’ gut bacteria Helicobacter pylori – a common cause of stomach ulcers and some cancers.
“We still have a long way to go before commercializing this technology,” cautions Westreich. “Yet, providing this positive trend continues in the next stages of research and development, we hope our plans for clinically approving the product will be fruitful soon.”